The present invention relates generally to electrical devices, and more particularly, to novel electrical circuits and to energy conversion devices embodying such circuits. The invention relates to circuits, devices and methods for changing both the voltage and the frequency of a given input signal, in a simple and straightforward way, into a signal of different voltage and frequency.
The devices are particularly suited to handling small to moderate amounts of power, and a typical device made according to the invention is lighter in weight, much more compact, and can be made at greatly reduced cost in relation to prior art devices intended for the same or similar purposes.
In addition to their inherent ability to create an output signal having a decreased voltage and an increased frequency in relation to the input signal, the devices are inherently capable of providing an output signal of a relatively stabilized voltage, which signal is relatively independent of the input voltage. The devices are therefore useful in a wide variety of applications wherein a closely regulated input voltage is not easily available, and in applications wherein a closely regulated output voltage is desirable. In many such cases, devices made according to the present invention are adaptable for use with input voltages which vary considerably; the devices are inherently able to provide highly stabilized voltage output signals even where the input voltage varies widely.
In certain applications, devices made according to the invention are able to use transformers which are much smaller and/or more efficient than those which would be required for counterpart prior art devices. In still other aspects of the invention, circuits made according to the invention are able to be combined with other known electrical circuits, and, in combination with such circuits are able to derive significant additional advantages in use such as providing greater efficiency, creating less waste heat in use, and the like.
In still other aspects, circuits are provided which, according to the invention, use single components for two purposes, that is, such circuits use elements required for the present invention to perform functions in addition to those provided for their primary purpose. In a number of applications, the invention provides circuitry which is greatly simplified in relation to prior art circuitry, and the invention thus provides means for making a number of commercial devices characterized by significantly lower cost and greater simplicity.
By way of example, the invention is able to be used to provide devices such as direct current power supplies, battery chargers, noise makers, such as those used in doorbells, annunciators, smoke alarms, and the like. Other commercial devices which advantageously embody the present invention include optical signalling devices such as light-emitting diodes driven with relatively intense high-frequency pulses, and the like. In still other applications, the signals created by circuits of the invention are used to drive piezoelectric devices, magnetostrictive devices or the like and these devices use the mechanical energy created thereby for operations such as ringing telephones or the like, thereby replacing heavy and expensive prior art magnets, bells, etc.
A typical circuit made according to the invention includes, in simple form, a bilateral, preferably electrically symmetrical, switch and a capacitor in series therewith, with a load being placed in series circuit relation relative to the switch and the capacitor, or placed in parallel or shunt relation across the capacitor.
In other forms, the switch may not be symmetrical, but instead may consist of a voltage or current sensitive switch having certain breakover characteristics in a forward direction and other breakover characteristics in an opposite direction. In typical applications, the load may either consist of the capacitor itself in series with the switch, or the load may be exterior of the switch and capacitor circuit, with such load being energized or driven by an element which is in mutually inductive relation to an inductor placed in series in the switch-capacitor circuit.
Where an inductor is in series relation with the switch and capacitor, the secondary inductor which is typically provided forms a part of a secondary circuit which may vary considerably in design, depending upon the application or end product sought to be obtained.
In another aspect, the invention makes possible the use of its inherent voltage lowering and frequency converting feature to reduce the size of a transformer needed for a particular application, and the reduction of transformer size may in turn be taken advantage of by incorporating the secondary of the transformer into a battery or other device where this is indicated for purposes of convenience.
As one example concerning reduction of transformer size, articles such as battery chargers or DC power supplies used for small appliances, instruments and the like may use a transformer which weights merely a small fraction of an ounce in contrast to transformers which weigh five to eight ounces or more and which are typically used to power articles such as tape recorders, small calculators, and the like. As an example of a device incorporating the transformer secondary into a part thereof, the present application describes a battery powered appliance having a rechargeable battery which is secured within the instrument, such as a radio or telephone signalling apparatus (a "pocket pager") and from which it is not desirable or necessary to remove the battery periodically for recharging. In this case, a small stand or the like is provided, with the stand unit containing the switch and capacitor elements of the invention together with the primary circuit portion of an output transformer. The stand unit is adapted to be plugged into a wall outlet. The pocket pager or the like includes a rechargeable battery therein, and the rechargeable battery includes a pair of charging leads electrically connected to the transformer secondary via a rectifier diode(s). The primary and secondary windings are arranged respectively in relatively flat planes and are disposed within the respective devices so that when the pager, radio or the like, rests upon the stand, the primary in the stand and secondary in the pager are brought into proximity although they are not connected by a metallic or galvanic connection.
When the pager or the like which contains the battery thus rests adjacent the charging device, the battery can be charged without removing the battery from the pager or connecting it to the charger. Batteries themselves, or articles containing them can therefore be charged in a matter of a few hours or less, or overnight, as preferred, merely by placing them in physical proximity to the charger which is preferably designed to receive and orient the product so that the primary and secondary coils are in the desired spatial relationship to each other.
Referring to another advantageous feature of the invention, it is common for power supplies used with small calculators and the like to include transformers which are relatively large in view of the power passed therethrough, such transformers being made in these sizes by reason of being called upon to transform relatively high voltages--110 to 220 v. at relatively low frequencies--50 or 60 Hz. Commercially available transformers of this type commonly include a switch and associated circuitry adapting the same transformer for operation with both 110 and 220 v. sources. The fifty cycle transforming operation requires a somewhat larger, heavier core, and consequently a transformer designed for both 50 and 60 cycle operation is unduly heavy if it is in fact used for 60 cycle operation only; on the other hand if a transformer designed for 60 cycle operation is operated at 50 cycles, it will be overlooked. According to the present invention, however, the size and weight of the transformer may be made so small as to be virtually insignificant. Because of the operating principle of the device, no switch is necessary to adapt the device to either 110 or 220 v. operation.
The invention relates also to a method of incrementally charging and discharging a capacitor in series with a voltage- or current-sensitive bilateral or like switch, periodically charging and discharging the capacitor in response to the ever-increasing or decreasing voltage level of the input signal.
While a very simple form of circuit made according to the invention will satisfactorily handle low or moderate power applications, modified forms of the circuit may also be made which can deal with larger amounts of power as well. While the device would normally be used with single-phase current, devices made according to the invention could also be used with three-phase or other current if and when there were some reason to do so.
Referring now to the general background of the invention, most electric power in the world is generated as alternating current in either a fifty or sixty Herz (cycles per second) frequency, and although the voltages used in long distance and local transmission of electric energy are often extremely high, such as several hundred thousand volts or more, the voltage ultimately made available at the point of typical usage is 100 to 270 volts AC for domestic and commercial customers, with perhaps somewhat higher voltages such as 440 volts being available to industrial customers. Unless stated or implied otherwise, such nominal AC voltages are the root mean square (rms) rather than peak voltage value of the signal.
A small, although still sizable, amount of energy is generated at other frequencies, and such as 16.6, 20, 25, 30, 33.3, 40, 42, 50,, 54, 60, 66, and 66.6 Hz, at voltages ranging from about 60 to 120 volts, for the purposes of ringing telephones, with interrupted 20 and 30 Hz ringing frequencies being perhaps the most commonly used for this purpose. In other cases, small but still significant amounts of power are generated at frequencies from about 400 Hz to 1,000 Hz, usually at 115 volts AC. For aircraft usage, 400 Hz is probably the most commonly used freqency.
The basic reason for generating energy at different frequencies may relate to the method of generating the current, or to certain requirements of the signal once generated. For example, multi-poled generators of the type used in electric utilities are extremely large, and peripheral velocity considerations tend to limit armature speeds such that cyclic generation in the order of 50 to 60 Hz. In the case of telephones, the lower frequencies were chosen to separate the signal and voice paths which customarily operate on the same pair of wires on each telephone subscriber line.
In the case of some of the higher frequencies, such as in aircraft and aerospace applications, efficiency, minimum size and minimum weight are highly important considerations; therefore, relatively high frequencies of 400 to 1,000 or even 10,000 Hz are generated in the first instance. These frequencies permit reduction in the relative size of the magnetic components of the apparatus, namely, they permit generator, motor and transformer components which are of greatly reduced mass relative to their counterparts using for low frequency magnetic induction as a part of their operation.
However, it is well known that although power is generated and distributed at certain characteristic voltages and frequencies, it is extremely common to transform such power and/or otherwise convert it into a signal which has greatly different characteristics, generally for reasons relating to the type of apparatus being powered.
More specifically, while a number of appliances and the like are powered by synchronous or other motors using 60 Hz, 110 volt AC, a significant amount of domestic alternating current is converted into direct current (DC). Such conversion to DC may take place to operate such articles as microwave ovens, tape recorders, calculators, television sets, etc., either within, partially within, or outside ofthe powered unit.
In view of the present need for simpler and more efficient electrical devices, it is an object of the present invention to provide a novel electrical circuit having a number of useful applications.
Another object of the invention is to provide an improved electrical circuit which is capable of use with other known circuits to provide a variety of useful devices.
A still further object of the invention is to provide improved electrical devices which utilize a given input frequency and voltage and which, in operation, produce or utilize a different output voltage and frequency.
Another object of the invention is to provide a device which is capable of subdividing an electrical input signal into a plurality of pulses having a reduced voltage with respect to the input voltage and a higher frequency than the input frequency.
Still another object of the invention is to provide an electrical device which is adapted to convert an input signal into an output signal characterized by carefully regulated output voltage.
Another object of the invention is to provide an improved electrical device which is highly efficient in use and which adapts itself to miniaturization for a larger number of applications.
Still another object of the invention is to provide an electrical circuit which may be used in a large variety of commercially useful devices, and which operates on a novel electrical principle.
A still further object of the invention is to provide an electrical device which can provide or use output signals having a reduced voltage and increased frequency with respect to the input signal, and which can achieve and produce such signal without the use of conventional inverters, vibrators, or the like.
Another object of the invention is to provide an electrical circuit which can be used to produce an improved direct current power supply.
Yet another object of the invention is to provide an economical and simple circuit adapted to power products operated by pulsating alternating or direct currents.
A still further and important object of the invention is to provide a device capable of operating with input voltages ranging widely, such as between 90 and 240 volt AC, for example, and having input frequencies ranging from 47 to 66 Hz and still characterized by a stable output voltage in spite of such variations of input voltage, frequency, or both.
A further object of the invention is to provide an improved power supply device which, when used in association with known power supply components, provides increased efficiency and other advantages in use.
Another object of the invention is to provide a battery charger having several highly desirable characteristics.
Another object of the invention is to provide various devices such as audio or visual annunciators or the like and which embody the novel circuit to provide useful functions at reduced cost.
Another object of the invention is to provide electrical devices which make possible the replacement of more expensive components when used in ringing devices such as doorbells, telephones, and the like.
Another object of the invention is to provide an electric circuit which may be advantageously used with magnetostrictive or piezoelectric devices, and which is characterized by improved simplicity and reliability in respect to prior art devices and circuits intended for the same purpose.
Still another object of the invention is to provide a simplified circuit which is adaptable to produce multiple, alternate output frequencies and to provide devices which use such frequencies for different applications.
A still further object of the invention is to provide an electrical circuit which includes a voltage- or current-sensitive switch device in series with a capacitor, with the circuit being adapted to be placed across an alternating current source to provide a number of desirable features and characteristics when used with an electrical load placed in series between the switch and the capacitor or, in some cases, in parallel or shunt relation to the switch.
Yet another object of the invention is to provide a circuit wherein the voltage of the output signal depends on the breakover voltage of the switch device rather than upon the voltage of the input signal.
A still further object of the invention is to provide a device which is able to produce an output signal of higher frequency and lower voltage than that of the input signal supplied to the device, and which creates greatly reduced stray magnetic fields by reason of using one or more transformers of greatly reduced size.
An additional object of the invention is to provide an electrical circuit which includes a bilateral switch and a capacitor in series with an inductive load placed in series with the capacitor and the switch.
A still further object of the invention is to provide a circuit having a bilateral switch, a capacitor and an inductor in series, and wherein the inductor is inductively coupled to a secondary circuit adapted to provide a variety of functions.
These and other objects and advantages of the invention, including those inherent therein, are achieved in practice by providing a circuit having voltage- or current-sensitive switch means in series with a capacitor, and wherein an electrical load forms a part of, or is placed in series or parallel relation with, such circuit.
The invention also achieves certain of its objects by providing a switch and capacitor in series, with an inductor in series relation therewith, and by providing various circuit elements in cooperative relation with such switch capacitor inductor.
The invention also achieves certain of its objects by providing a simplified apparatus and method for subdividing an input signal into a plurality of pulses of current characterized by reduced voltage and increased frequency with respect to those characterized of the input signal.
The exact manner in which these and other objects and advantages of the invention are attained in use will be more clearly apparent when reference is made to the detailed description of the preferred embodiments of the invention set forth by way of example and shown in the accompanying drawings, in which like reference numbers indicate corresponding parts throughout.